OFFSET
0,5
COMMENTS
The meandric numbers A005316 are the numbers of paths which cross themselves 0 times.
This sequence is the number of paths that must cross themselves exactly twice.
LINKS
B. W. J. Irwin, On the number of k-crossing partitions
EXAMPLE
a(4) = 8; this is from the partitions
(2,1,4,3), (2,4,3,1),
(3,2,4,1), (3,4,2,1),
(4,1,3,2), (4,2,1,3),
(4,2,3,1), (4,3,1,2).
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Benedict W. J. Irwin, May 22 2017
STATUS
approved